Generally, in a stabilizer rod supporting structure, the torsion section of the stabilizer rod is extended in the lateral direction, a bush is fitted into each of left and right end parts of the torsion section, and each of the bushes is mounted on the vehicle body interposed by a mounting bracket. By mounting each of the bushes on the vehicle body, the stabilizer rod is mounted on the vehicle body interposed by the bushes. The stabilizer rod has an arm section provided to the left and right end parts of the torsion section, and left and right suspension units are provided to the left and right arm sections.
Known stabilizer rod supporting structures include ones in which a polygonal ring is fixed to the left and right end parts of the torsion section, a bush is provided adjacent to the polygonal ring, and the end part of a sleeve provided to the bush is engaged with the polygonal ring (as disclosed in, e.g., Patent Document 1).
Having the end part of the sleeve be engaged with the polygonal ring connects the torsion section and the bush so that the torsion section and the bush do not rotate relative to each other. Therefore, when the torsion section twists, the torsion section and the bush are prevented from rotating relative to each other, and the sleeve is inhibited from slipping relative to the torsion section. However, the support structure disclosed in the abovementioned Patent Document 1 involves the need for the polygonal rings which are fixed to the left and right end parts of the torsion section and the sleeves which are engaged with the polygonal rings, and therefore requires a larger number of components, impeding efforts to minimize cost.
Known stabilizer rod supporting structures also include ones in which an outer frame of a bush supporting the left and right end parts of the torsion section is formed from a base material and an inner periphery part (hereafter referred to as a surface layer) is formed on the inside of the base material from a highly slidable rubber (as disclosed in, e.g., Patent Document 2). Thus, forming the surface layer of the bush from a rubber exhibiting high slidability (i.e., “highly slidable rubber”) and causing the highly slidable rubber to engage with the left and right end parts of the torsion section make it possible to reduce the sliding resistance acting on the torsion section.
Accordingly, causing the highly slidable rubber to engage with the left and right end parts of the torsion section makes it possible to reduce the sliding resistance between the bush (highly slidable rubber) and the torsion section when the torsion section is twisted. This makes it possible to suppress stick-slip sounds generated when there is a slippage between the torsion section and the bush.
However, the bush in Patent Document 2 is formed so that the surface layer (highly slidable rubber) of the bush has a large thickness substantially equal to the wall thickness of the base material. With the highly slidable rubber, slippage of the base material increases, as does hysteresis in the bush, in order to reduce the sliding resistance. Therefore, forming the surface layer (highly slidable rubber) of the bush so as to have a large thickness substantially equal to the wall thickness of the base material makes it more difficult to impart the bush with spring characteristics.